This invention relates to spot welding guns and, more specifically, to a spot welding gun having replaceable, multipurpose, adaptable electrode holders.
Resistance or spot welding joins metal sheets or structures through heat produced by resistance to the flow of electrical current. The metal structures to be welded are clamped together with rod-shaped electrodes applying pressure on opposite sides. An electric current passed between the electrodes meets resistance when it flows across the metal structures, producing heat that melts the metal and welds them together. No filler metal or flux is used.
Conventional spot welders use a gun having two electrode holders, one fixed and the other moveable, extending from a handle, adapted to pinch together in the manner of pliers along a line approximately perpendicular to the handle axis. The pinching force may be applied manually or by a pneumatic cylinder, electrical solenoid or the like. The spot welding gun is connected to a welder power supply through heavy cables carrying the high amperage current necessary for welding and to a source of air or electricity for applying the pinching force.
A number of different welder and electrode configurations have been developed for special purpose welding. While effective for simply welding metal sheets together along an edge, or for a single specific arrangement of metal structures, these devices are not adaptable to the wide variety of applications necessary in repair work, in particular auto body repair work.
In a many cases, it is necessary to spot weld at locations well away from the metal edges. Often welds must be made in areas having large or thick structures between the edge of the structure and the area to be welded. It is difficult and expensive to construct or assemble a special spot welder for each of these difficult situations.
Thus, there is a continuing need for multipurpose, easily adaptable, spot welding guns having electrode holders with the capability of welding at a variety of locations.